In an effort to develop a successful immunotherapy for intraocular tumors, we have examined previously the cellular mechanism that prevents cytotoxic T cells from eliminating tumor cells growing progressively within the anterior chamber of mouse eyes. Our results indicated that tumor-infiltrating precursor cytotoxic T cells (pTc) failed to terminally differentiate into cytolytic T cells that lyse tumor cells. The failure to initiate pTc differentiation resulted from (i) incomplete activation of specific T helper cells that secrete lymphokines (IL-2 + IL-4) required by pTc, and (ii) suppression of Th activity by the local microenvironment within the eye. In these proposed experiments we will extend these studies by using a form of gene therapy to manipulate this failed immune response to eliminate established ocular tumors and provide long-term protection from a second tumor challenge. Recent data from other laboratories indicates cytotoxic T cells are activated directly in the absence of T helper cells in mice treated with tumor cells transfected with cDNA for either lymphokine genes or the B7 molecule. In the present series of experiments we will use a novel vector system (nonretroviral) to transfect tumor cells that, when reinoculated into mice, activate directly tumor-specific cytotoxic T cells and bypass the requirement for T helper cells. We hypothesize that tumor cells transfected with cDNA for either lymphokine genes (IL2+IL4), or B7 will induce tumor-specific cytotoxic T cells that eliminate established ocular tumors and providing long-term protection from a second tumor challenge. The specific aims of this project are to (i) determine if cDNA transfected tumor cells are rejected from syngeneic mice and induce protective immunity to untransfected tumor cells, (ii) determine the mechanism of protective immunity induced by treatment with transfected tumor cells, and (iii) determine if altering the local immunosuppressive environment within the eye by intra-ocular injection of either IFN-gamma or lL-12 facilitates T cell mediated rejection of ocular tumors. The experiments described in this grant will provide the basis for future experiments that will utilize this form of gene therapy for the treatment of human intraocular tumor patients.